wifi: rtw89: refine scan function after chanctx

Since we can get the current channel definition each interface maps to,
remove store_op function that is no longer required to make things simple.

Signed-off-by: Po-Hao Huang <phhuang@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230415034900.15679-3-pkshih@realtek.com